Although physical activity is routinely prescribed for military-eligible women, a systematic examination of the effects of different modes of training on women's physiology and work performance has not been undertaken. Specifically, the decline in physical activity and loss of fat-free mass are significant predictors of decreased function and increased cardiovascular risk in military-eligible women. Thus, exercise interventions specifically designed to offset these deleterious changes in work performance, body composition and physical activity are important considerations. All military women initially experience the physical challenges of basic training and once through this experience, the new soldier experiences additional physical challenges that are directly influenced by other military-related activities including, deployment, natural aging, etc. Moreover, given the increased number of career military women retained in the services, strategies to achieve and maintain optimal fitness are of high priority. The overall hypothesis is that the decline in physical activity habits and resultant increase in body fat reduce exercise capacity and muscle mass in military women. These lifestyle changes worsen metabolic and cardiovascular risk factors. Therefore, continued involvement in resistance and endurance exercise programs which increases or preserves fat-free mass will prevent functional declines in military-eligible women. Although exercise is frequently recommended to enhance overall fitness, it is unclear as to whether endurance or resistance exercise is more effective in attenuating functional and cardiovascular declines in women. We will systematically compare the effects of endurance and resistance exercise on physical activity, cardiovascular fitness, and fat metabolism in military eligible women. The results of this study will lay the groundwork for appropriate exercise prescriptions to reduce cardiovascular and metabolic risk and enhance physical function in military-eligible women. To date we have screened via telephone over 300 women for the study. From those, 97 volunteers met inclusion and exclusion criteria and were invited for the screening visit at the Clinical Research Center (CRC). To date, 71 women were invited for the first overnight visit at the CRC. Starting in February 1997, volunteers began exercising at the Racquets Edge Health and Fitness Club using the exercise prescription described previously. To date, we have introduced 25 volunteers into the endurance training group, 27 to the resistance training group, and 19 to the control group. So far, 12 members of the endurance-training group, 11 of the resistance-training group, and 18 from the control group have completed the intervention period and undergone the second overnight visit. In the future, we will continue to screen interested women. Those who meet the inclusion criteria will be invited for the baseline testing. Furthermore, we have currently 10 women in different stages of the intervention period and hope to post-test them during the first half of 1999.